Ignition coil



Feb- 8, 1955 R. F. GETz ETAL 2,701,865

IGNITION COIL Filed May 5l, 1952 2 Sheets-Sheet l Feb. 8, 1955 R. F. GETz ,ETAL 2,701,865

v IGNITION COIL Filed May 51, 1952 2 sheets-sheet 2 jNl/ENTORS /f wma' BY @M 0PM a United States Patent() 2,701,865 IGNITION COIL Raymond F. Getz and August Toelle, Detroit, Mich., assignors to Essex Wire Corporation, a corporation of Michigan Application May 31, 1952, Serial No. 291,014 9 Claims. (Cl. 336-96) This invention relates to an ignition coil and is an improvement upon the coil disclosed and claimed in the copending application of Arni Helgason, Serial No. 763,898, tiled July 26, i947, which is now abandoned. ln the above identified application, there is disclosed an ignition coil having a magnetic circuit with air gaps which are small as compared to conventional ignition coils. Such a coil requires substantially less copper for the same output.

The coil described and claimed in said application, generally comprises a straight central magnetic core portion over which are disposed a secondary and a primary in the order named, the primary being on the outside. A second core part consists of laminations disposed along the outside of the primary and has end portions bent around the sides of the winding and extending toward the straight core portion. The two parts of the magnetic core are respectively at high and low potentials, insulated from each other and maintained in predetermined relation by suitable insulating structures.

The invention hereinafter disclosed and claimed embodies the highly desirable advantages and features of the Helgason construction. The new construction generally has straight centrally-disposed laminations forming one part of the magnetic circuit. The other part of the magnetic circuit consists of a plurality of groups of laminations lying along the outside of the windings with the end portions of the laminations bent inwardly toward the center or axis of the coil. The coil has a secondary winding disposed immediately adjacent the central magnetic core portion. Around the outside of the secondary is a primary winding and this primary winding preferably, though not necessarily, has the ends thereof extending short of the ends of the secondary winding structure. Disposed at the two ends of the windings are insulating structures. These insulating structures include spaced projections which are adapted to engage the sides of the coils, in this case the primary winding.

By virtue of this construction, a skeleton construction of prefabricated insulation is provided, said construction providing passageways from the outside of the windings to the interior through which liquid insulation may iiow. The insulating structure for the bottom of the coil encloses the free end of the straight magnetic core portion. This bottom insulator has projections at the bottom of the insulator which raise the main body of the insulator from the bottom of the casing for the coil structure.

Both insulators are so designed that no unduly thick walls are provided whereby dense and compact molded insulation may be provided. Inasmuch as the insulators at the two coil ends must withstand the full diierence in potential of the secondary of the coil, it is of the utmost importance that excellent insulation characteristics be made possible economically in quantity production of such insulators.

The insulator construction at the two ends of the coil provides a minimum amount of prefabricated solid for insulation while still fullling the mechanical requirements of spacing the high tension inner core part and the low tension outer core part. The construction is such that considerable space is left into which liquid insulation may flow, thus supplementing the insulation aiorded by the prefabricated rigid insulating members. Thus by virtue of the design of the insulators, the distances through various parts of the insulator in some direction are kept small, although in other directions the distance may be suiciently great to provide full and complete high tension insulation.

Both insulators are so designed that they cooperate respectively with the two magnetic core portions so that the outer laminations may be disposed easily, quickly and accurately in position.

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The completed coil may be slipped into a metal can and potted with oil or insulating compound in the usual fashion. By virtue of the construction, air pockets are eliminated and adequate insulation is provided. At the same time, the design of the prefabricated insulators is such that quantity production of said insulators is easily attained.

ln order that the invention may be understood, it will now be explained in connection with the drawings, wherein exemplary forms, illustrating the invention, are dis closed. It is understood that the forms shown in the drawing are merely exemplary of the invention and that numerous variations in construction are possible without departing from the spirit of the invention.

Referring therefore to the drawings:

Figure 1 is an exploded view of the top and bottom insulators with the windings between the insulators of a coil embodying the invention;

Figure 2 is a sectional elevation on line 2-2 of Figure 3;

Figure 3 is a plan view of the coil illustrated in Figure 2;

Figure 4 is a sectional view on line 4-4 of Figure 2;

Figure 5 is a sectional elevation similar to Figure 2 as far as the container and insulating cap are concerned and a simple elevation of the coil proper showing the magnetic core portions in position;

Figure 6 is a section along line 6-6 of Figure 5; Figure 7 is a section along line 7--7 of Figure 5', Figure 8 is a section along line 8-8 of Figure 5; Figure 9 is a perspective detail of a group of laminations forming a portion of the magnetic core structure',

Figure l0 is a section of a modified form of insulating cap combined with an insulating sleeve for going over the projecting end of the inner portion of the straight laminations;

Figure ll is a perspective View showing the bottom of the top insulator for the coil.

Referring first to Figures l to 9 inclusive, the new ignition coil comprises concentric windings 10 and 11. Winding 10 is the secondary and winding 11 is the primary and is disposed around the outside of winding 10. The windings are generally conventional in having the proper gauge wire and having adjacent layers separated by waxed paper or thin sheets of suitable insulating material, the paper extending beyond the end turns of each wire layer.

Secondary 10 has high potential lead 12 while primary 1l has lead 13. Both primary and secondary have common leads 15, this functioning as the low potential lead for the secondary. As a rule, lead 15 will be grounded while lead 13 will be connected to a terminal of a battery. As far as secondary potentials are concerned-and these may range from 10,000 volts up to as high as 25,000 volts-leads 13 and 1S are both substantially at ground. ln practice, the battery potential between leads 13 and 15 will be comparatively low and may range anywhere from about 6 volts up to possibly 24 volts. Momentary diiierences or surges of potential somewhat in excess of these Values may be developed when the battery circuit is opened.

Primary winding 11 is shorter in length than secondary winding 10 to leave secondary portions 17 and 18 extending beyond the ends of the primary windings. ln practice, it may be that only the paper sheets of the f secondary extend that far.

It is preferred to have primary 11 wound separately from secondary winding 10, the primary thereafter being slipped over the secondary. Thus different ignition coils may be provided by matching or combined desired windings. It is understood that common lead 15 will consist of the two adjacent leads from the primary and secondary, the two leads being twisted together.

Primary winding 10 has a generally cylindrical bore 20 within which is disposed one part of the ferromagnetic core consisting of a stack of straight laminations 22. suitable steel, these generally being of silicon steel, with the ends cut square as shown in Figure 2. A number of these laminations are bundled together to form a group having a generally rectangular cross section, as shown in Figures 6 and 8, for example. In order to These laminations may consist of long strips of` utilize the internal space within the secondary winding, it is possible to have a rectangular bore to provide a snug tit for the laminations. In general, however, it is easier to Wind on a mandrel or form having a circular section and the Wasted space along the sides of the laminations are of no great consequence. Furthermore, there will be no necessity for orienting the secondary winding with respect to the stack.

Cooperating with the primary and secondary windings, at the two ends thereof, are prefabricated insulators 24 and 25. These insulators may be conveniently molded out of suitable material, such as Bakelite. glass, ceramic, or any of the insulating materials having suitable insulation characteristics. inasmuch as these insulators must withstand the full difference of secondary potential, it is necessary that the material of which the insulators are made have satisfactory insulation characteristics.

While the ignition coil may be used in any desired position, it will be advantageous to consider the normal coil position as shown in Figure 2, with the top of the coil at the top of this figure and the bottom of the coil at the bottom of this figure. Thus insulator 24 may be considered as the top insulator. This comprises hat body 27 which may be considered as being originally of a square shape. Thus body 27 has undercut or indented sides 28, there being four such sides, and also has shorter sides 29 which may be considered as having been derived by clipping corners. The top insulator as a whole may be said to have eight sides with under-cut sides 28 forming one group and projecting sides 29 alternating with sides 28 to form the other group.

Under-cut sides 28 are bounded at the ends by walls 30 and 31 while projecting sides 29 are provided at the center with a generally U-shaped notch 33. The central portion of body 27 has a generally circular cut-out 34.

Top insulator 24 has outer face 34 and inner face 35 (see Fig. 1l). Outer face 34 is generally flat while inner face 35 is provided with a number of embossings 36. Embossings 36 are preferably distributed symmetrically on the inside insulator face and are disposed at the centers of under-cut sides 28, extending inwardly toward the center of the insulator. Additional embossings may be provided, or the number of embossings may be reduced to three, if desired. The location of the emboss ings is not important. The location of notches 33 is also not important as long as they clear sides 28. These notches are provided for accommodating leads 13 and 15.

Each embossing 36 has two steps 37 and 38 respectively, the lower step 37 being inwardly disposed with respect to higher step 38. height of the steps will be governed by the dimensions of the windings as will be apparent. Thus as shown in Figures 2 and 5, insulator 24 is adapted to overlie the top end of the coil windings. Inner step 37 normally lies on the edge, or side, of primary while outer and higher step 38 engages the side of primary 11. The actual step itself consisting of the portion of the insulator between parts 37 and 38, may lie along the outside of projecting portion 17 of the primary. Thus insulator 24 may be disposed upon the ends of the windings, to engage the primary and secondary windings, the steps spacing body 27 of the insulator away from the sides of the primary and secondary windings. This feature is advantageous in that access of liquid insulation under body 27 of the insulator and between the layers of sheet insulation to the windings is provided.

Bottom insulator has inner face 40 having the same general shape and contours as top insulator 24. Thus the bottom insulator has straight sides 28 and sides 29' derived from corners. lt will be noted that sides 29 are not provided with notches corresponding to 33 in insulator 24. These notches may be provided in the bottom insulator although they would serve no useful function. Bottom insulator 25 also has embossings 36' with lower and higher stepped portions 37' and 3S corresponding to the embossings in the top insulator. The top and bottom insulators also center themselves with respect to the windings.

Lower insulator 25 has well portion 42 extending downwardly from the outer face thereof. Well 42 has a generally square cross section and may have a taper for proper draw in molding. Well 42 has enlargements at corners, these enlargements being shown by numerals 43. Enlargements 43 (see Fig. 7) extend the full length of the wells from the body of the insulator down to the 85 The radial dimensions and bottom of the wells and beyond to provide feet 44. These feet extend below bottom wall 45 of the well.

As is shown in Figures 2 and 5. bottom insulator 25 has inner face 40 fitted against the bottom ends of the primary and secondary windings in exactly the same relationship as the inner face of top insulator 24. Additionaliy, well 42 encloses the lower part of inner laminations 22.

Cooperating with inner laminations 22 are a number of groups of outer laminations, here shown as four, each group being indicated by numeral 47. Thus, a group of outer laminations 47, may consist of a number of nested strips, there being three illustrated in Figure 9, merely by way of example. For convenience in stamping these laminations, each of the group may be similar in length and the three as a group may be bent simultaneously as shown in Figure 9. lf desired, the lengths of the individual laminations may be adjusted so that the other laminations are longer thus permitting the free ends of all the laminations to register. This, however, is not essential.

As shown, group 47 has the laminations bent to form end portions 48 and 49 connected by bent intermediate portion 50. The laminations for the outer group are dimensioned in width so that they may snugly fit at straight sides 28 and 28' of the top and bottom insulators. The insulators are shaped to provide guideways for the outer laminations. The length of the outer group is adjusted so that each group may be sprung into the position shown in Figures 2 and 5, end portions 48 and 49 of each group being adapted to lie along the outer edges of the top and bottoni insulators. Well 42 in the bottom insulator preferably has the inside thereof so proportioned that at the very bottom, the internal well dimensions are just large enough to accommodate the end of the laminations 22, properly oriented.

Since the top and bottom insulators must be angularly aligned because of the outer laminations, the top insulator will thereupon have its angular position determined. Thus the location of the groups of outer laminations will be determined with reference to the orientation of the inner laminations. When the outer laminations are sprung into position, as shown in Figures 2 and 5, the non-magnetic gaps between the ends of the outer laminations and the inner laminations will be predetermined. It is noted that the ends of the inner laminations extend substantially beyond the proiection of the bent ends of the outer laminations. Thus magnetic fringing reduces the effective gap reluctance and permits a larger gap to be used.

Well 42 provides insulation around the bottom ends of the outer laminations. The inner laminations are at high potential while the outer laminations are at or near ground potential. Hence the full difference of secondary potential is impressed across the non-magnetic gaps.

In order to provide adequate insulation for the upper portion of inner laminations 22, the form of the invention shown in Figures 1 to 5 inclusive has insulating sleeve 52. The sleeve surrounds inner group 22 of the laminations and extends down to the side of secondary 10. lt will be noted that inner cut-out 34 of top insulator 24 is substantially larger than the inside diam' eter of secondary 10. The height of the steps upon the inside faces of both the top and bottom insulators is sufficiently great so that the tips of outer laminations are spaced a substantial distance from the sides of the primary and secondary windings as measured parallel to the axis of the coil. Furthermore, the dimensions of bent portions 48 and 49 of each group of outer lamina.- tions overlie only a few of the outer layers of secondary 10 and do not overlie the inner layers of the secondary. inasmuch as the inner secondary layers are at increasingly higher potential, with respect to ground, it will be seen that the distance from the tips of the outer grounded laminations becomes increasingly greater with respect to the end turns of inner wire layers on the secondary.

As has been previously pointed out, secondary 10 is wound in conventional fashion with intervening sheet insulation between adiacent wire layers extending beyond the end turns for each wire layer. If desired, the secondary winding may be wound so that as the layers progress from the outside toward the inside of the secondary, the number of wire turns to the layer and thus the axial length of a layer decreases. Thus, as the potential of the end turns rises, with respect to ground,

the distance of the end turns from the paper edges also increases, providing additional insulation.

The construction so far described, may be assembled and temporarily maintained in position by tape or string around the outer lamination groups. In this condition, the coil consists of inner and outer groups of laminations, top and bottom insulators and primary and secondary windings. This may be tested preliminary to tinal assembly in a can. The `windings may be given an insulation test, the entire coil may be given an inductance test and it is even possible to immerse the unit in oil and operate the same at full potential.

Assuming that the coil proper is satisfactory, the assembly may now be disposed in metal can 60. Can 60 has ilat bottom 61 and an open top. Insulation in liquid form is poured into the can, either before or after disposing the coil assembly into the can. Due to the open construction of the coil and preiabricated insulators, normal potting of the coil is possible. Thus air bubbles can rise from the bottom of weld 42 and liquid insulation can penetrate into the insulation layers of the windings. The resulting coil will not have any air bubbles or voids.

With the level of the liquid insulation at a satisfactory height, the coil top may now be applied. The coil top comprises molding 63 of insulation having metal ferrule or flange 64. Top 63 has depending annular tlange 65 and upwardly extending annular flange 66. Flange 66 is eccentric of the top and has apertured metal contact cup 67 molded in the bottom thereof. Top 63 also has terminal screws 68 and 69 molded therein. Leads 13 and 15 are threaded through apertures in the terminal screws while lead 12 is threaded through the aperture in Contact cup 67. Leads 13 and 15 are positioned in two of notches 33 in the top insulator and the top may now be pushed down into position as shown in Figures 2 and 5. The various leads are soldered in place and excess lead length cut off. Prior to the soldering of the leads to the top terminals, air and excess insulation will be discharged through the top at the spaces around the lead wires. As shown in Figures 2 and 5, depending ilange 65 tends to telescope over sleeve 52. If desired, one or more apertures through sleeve 52 may be provided for access of liquid insulation to the sleeve interior.

It will be clear that the constants of the ferromagnetic circuit of the coil will in no way be affected by disposing the coil assembly within can 60. Usually the can will be of sheet iron. The outer groups of laminations do not have their positions, with respect to the inner laminations, affected. This is true even though the bent portions 50 of the outer laminations may tit very snugly within the can. The can itself may be lined with paper, if desired, to provide a moderate degree of insulation for battery potential with respect to ground of the outer laminations.

Instead of having undercut or indented sides 28 for the prefabricated insulators, the outer face may have embossings or protuberances to act as guides for the sides of the bent end portions 48 and 49 of the outer laminations. Thus in all cases, the groups of outer laminations will tend to lock the prefabricated insulators into position. Bottom insulator 40 may be similar to top insulator 24 in not having a well. In such case, the central cut-out may be square and provide a snug fit for the central stack to prevent turning oi the stack. The well is desirable, however, because it acts to support the central laminations against falling through during preliminary assembling and testing. Furthermore, the well bottom retains the central stack in position during potting.

Top insulator 24 may have a cut out at the center to t snugly around the central stack. Thus the top and bottom insulators will not only be angularly oriented but also centered with respect to the windings. Additionally, the embossing step may engage the outside of the primary to aid in centering the insulators. In such case, the outer or high embossing step will be on the cylindrical surface of the primary. Sleeve 52 and depending ange 65 may be combined into one as shown in Figure l0.

What is claimed is:

1. An ignition coil comprising a secondary winding, a primary winding around said secondary, the inner secondary terminal being at high potential and the remaining terminals being at relatively low potential, prefabricated insulators for the winding ends, there being one insulator for each end of the coil with the insulator being disposed against the ends of the windings, each insulator having embossings for engaging the winding ends to center and space the main body of each insulator from the ends of the windings, a stack of straight laminations extending through the secondary center and having end portions projecting beyond the winding ends, a plurality of similar groups of outer laminations, each group having the ends bent to form a shallow general U shape, each group disposed lengthwise along the outside of the primary with the bent ends extending along the primary sides toward the projecting portions of the straight stack, means on said prefabricated insulators for supporting the various laminations so that the groups of outer laminations are disposed in predetermined oriented positions with respect to each other and the central stack thereby to provide a coil with predetermined nonmagnetic gaps.

2. The construction according to claim l, wherein said straight stack has a rectangular cross section and wherein one of said prefabricated insulators has a portion thereof at the center through which the straight stack passes and is retained against turning.

3. The coil according to claim l, wherein the primary winding is shorter than the secondary winding to leave projecting secondary winding end portions extending beyond the primary winding at each coil end and wherein said embossings engage the said projecting secondary portions for centering the pretabricated insulators with respect to the windings.

4. An ignition coil comprising a secondary winding, a primary winding around said secondary, the inner secondary terminal being at high potential and the remaining terminals being at relatively low potential, flat prefabricated insulators disposed against the ends of the windings, each insulator having embossings for engaging the winding ends to center and space the main body of each insulator with respect to the ends of the windings, a stack ot straight laminations extending through the secondary center and having end portions projecting beyond the winding ends, one of said insulators having a well portion into which one of the projecting stack portions extends, a plurality of similar groups of outer laminations, each group having the ends bent to form a shallow general U shape, each group being disposed lengthwise along the outside of the primary with the bent ends extending along the primary sides toward the projecting portions of the straight stack, means on said prefabricated insulators for supporting the various laminations so that the groups of outer laminations are disposed in predetermined oriented positions with respect to each other and the central stack thereby to provide a coil with predetermined non-magnetic gaps.

5. The ignition coil according to claim 4, wherein each prefabricated insulator has guideways formed therein into which the outer lamination groups are disposed for orienting the same.

6. The ignition coil according to claim 4, wherein each insulator has under-cut portions at the edges thereof for guiding the outer groups of the laminations.

7. The ignition coil according to claim 4, wherein said well portion has feet extending downwardly therefrom and wherein said coil is disposed in a metal can and wherein said coil is potted in said can with insulation, said insulation being run in as a liquid and lying along the bottom of the can and filling the space below the well.

8. The coil according to claim 4, wherein the upper portion of the central stack extending beyond the end of the secondary winding has an insulating sleeve disposed over the same.

9. The ignition coil according to claim 4, wherein said coil is disposed in a metal housing having au open top with the coil standing up in said housing and wherein said can has a molded insulated cap covering the same, said insulating cap being provided with a downwardly extending annular flange surrounding the upwardly projecting portion of the central laminations.

References Cited in the file of this patent UNITED STATES PATENTS 2,327,784 Hartzell s- Aug. 24, 1943 2,512,796 Hartzell June 27, 1950 FOREIGN PATENTS 352,783 Great Britain July 16, 1931 

